TRANSPORTATION COMMITTEE 11 FEBRUARY 2009 SPINAL ROUTE IMPROVEMENTS Report by Director of Technical Services

PURPOSE OF REPORT To inform Members of the progress made to date highlighting any

issues that have a bearing on the delivery of the programme. COMPETENCE 1.1 There are no legal, financial or other constraints to the recommendations being

implemented. SUMMARY 2.1 Capital Programme 2008 – 2012 At the October 2008 series of committee meetings the Comhairle recommended that

Technical Services progress the designs of the first four schemes in the prioritised list. The length of each improvement was to be reduced to approximately 1km to enable four schemes to be delivered from the £3.75m budget.

2.2 The design brief for all the schemes is summarised below:

• Provide a 6.6m wide carriageway utilising, where practicable, the horizontal alignment of the existing road.

• Ensure tie in points of the improvements do not create new hazards for road users. 2.3 Topographic survey and ground investigation work has been carried out at each location

to allow the development of preliminary designs and construction cost estimates to be made for each scheme. A description of the existing sites and potential construction problems that need to be resolved on each is given in the following sections of the report.

2.4 Cost estimates and a summary of principal quantities for each scheme are included as

an appendix to this report. Drawings showing the preliminary designs and a draft programme for the delivery of the schemes will be on display prior to the committee.

2.5 The preliminary assessment of the first four projects on the Spinal Route prioritised list has shown that the schemes in Carinish and Leverburgh are the more complex of the four and consequently they will take longer to design out the financial, engineering and environmental risks. The current economic climate has highlighted the importance of swift procurement of civil engineering projects in order to sustain that sector of the local economy in the short term. Therefore, it seems prudent to progress the more straightforward schemes first, allowing more time to be spent on designing the more complex schemes while maintaining the flow of work to the local economy. It is proposed to deliver the programme in the following order:

1. A859 Stockinish Junction to Luskentyre Junction 2. A865 North of Kildonan Junction to Loch Roinich 3. A865 Carinish Hall to Carinish Village 4. A859 Kyles Lodge Entrance to Leverburgh Village RECOMMENDATION 3.1 It is recommended that the Comhairle note the progress made on the Spinal Route

Programme and agree to the proposed amendment to the order of delivery of the schemes.

Contact Officer: Colin MacIver, 01851 709485 Appendix: Cost Estimates

BACKGROUND

A859 Stockinish Junction to Luskentyre Junction

4.1 The Terrain in this area is extremely rocky moorland with minimal vegetation and lies within the “South Lewis, Harris & North Uist National Scenic Area”. With the exception of occasional isolated pockets of peat there is little unsuitable material (peat/moraine) covering the bed rock. There are four significant watercourses crossing the line of the existing road, all of which are susceptible to flash flooding due to the steep rocky nature of the surrounding catchment area.

4.2 The section of road to be improved extends for approximately 1km in a southerly direction from the existing double track section of road at the junction to J. Mackay’s quarry. The geometry of the existing single track road is reasonably good although the southern end of the section would benefit from some horizontal realignment. The main problem with the existing road is the poor vertical geometry and rock outcrops/cuttings obstructing forward visibility.

4.3 A second, smaller section of road (approx 400m) further south is also being investigated as an additional improvement. The existing section has poor horizontal and vertical alignments and crosses a significant watercourse. Forward visibility is further obstructed by an existing rock cutting. This section would benefit from a realignment of the road which would improve visibility and also generate rock from the widening of the existing rock cut.

Construction Issues

4.4 There main construction issues for this section is likely to be disruption to traffic passing through the site while rock blasting is taking place, however this should pose little difficulty to experienced Contractors. Mitigation measures and method statements will be submitted for approval prior to work commencing.

A865 Carinish Hall to Carinish Village

5.1 The terrain in this area is generally flat and incorporates a mixture of improved croft land and rough grazing moorland. The ground conditions are generally peat overlying moraine overlying bed rock. An average peat depth of approximately 3m has been measured on site however there are significant areas with depths in excess of 5m. The section of road lies outwith the “South Lewis, Harris & North Uist National Scenic Area”.

5.2 The section of road to be improved extends for approximately 750m in a northerly direction from the existing double track section of road at Loch nan Clach. The geometry of the existing single track road is reasonably good although the northern end of the section would benefit from some vertical realignment.

Construction Issues

5.3 The ground investigation already carried out has highlighted a significant hazard that will need to be “designed out” to enable the scheme to be built safely. The deepest sections of peat (more than 5m) are located directly adjacent (and possibly underneath) the existing road. To create a 5m deep excavation adjacent to a road carrying “live” traffic is highly likely to destabilise its foundation and runs the risk of a catastrophic failure of the existing road during the construction phase.

5.4 The problem of deep peat is compounded by the fact that there is no useable rock source on site meaning that all rock fill material will have to be imported from quarries off site, approximately 14km round trip.

5.5 An additional problem linked to the deep peat is finding an appropriate location to landscape the excavated material. The estimated quantity of excavated peat/clay of almost 27,000m3 would cover 4.5 football pitches with a 1m thick layer of peat.

A865 North of Kildonan Junction to Loch Roinich

6.1 The terrain in this area is generally rough grazing moorland, the northern part of the site is on higher rockier ground while the rest of the site is low lying and poorly drained. The ground conditions are generally peat overlying moraine, overlying bed rock. An average peat depth of approximately 1.5m has been measured with isolated pockets of up to 5m depth encountered.

6.2 The section of road to be improved extends for approximately 800m in a northerly direction from the south side of the Kildonan junction to the double track section of road at the War Memorial. The horizontal geometry of the existing single track road is good although the northern end of the section would benefit from some realignment. The vertical geometry however is very poor with a blind summit and various sharp crests and hollows in the existing road.

Construction Issues

6.3 The very poor vertical alignment of the existing road makes a simple “on line” widening improvement impractical if an improved vertical alignment is to be achieved. In order to remove the blind summit and build a two lane structure over Abhainn Charataig it is likely that the line for the new road will have to be built alongside the existing road over most of the northern half of the improvement. Although there is a significant quantity of peat/clay to be excavated there are suitable areas both on and off site that could be used to landscape that material.

A859 Kyles Lodge Entrance to Leverburgh Village

7.1 The terrain in this area is generally rough grazing moorland, the site runs along the length of Leverburgh Glen. The ground conditions are generally peat overlying moraine, overlying bed rock. An average peat depth of approximately 1.5m has been measured with isolated pockets of up to 5m depth encountered.

7.2 The section of road to be improved extends for approximately 1km in a southerly direction from the double track road at the Kyles Lodge junction to the widened section of road at the No.3 Leverburgh. The horizontal geometry of the existing single track road is reasonable as it descends down the Glen although the southern end of the section, as it enters Leverburgh village would benefit from some realignment. The vertical geometry is also very poor as the road enters Leverburgh and would benefit from realignment.

Construction Issues

7.3 The topography of Glenn Coishletter itself is a significant constraint to any improvement of the road. The existing single track road hugs the bottom of the steep side of the Glen, any excavation of the slope would result in a significant amount of slope stabilisation work being necessary. This problem is compounded by Abhainn Coishletter which runs parallel to the existing road for some 350m. Impacting a watercourse over that distance will require close involvement from SEPA when preparing the design and mitigating the impact to ensure that the CAR regulations are complied with.

7.4 The existing road is very poorly founded as it enters Leverburgh, Abhainn Coishletter drains in to a flat, very boggy area at this location. There is clear evidence of differential settlement cracking on the existing road here and Technical Services Roads Maintenance section have regularly resurfaced this spot over several years. Constructing a well founded road through this section will require further detailed investigation of the ground conditions and assessment of appropriate construction techniques that could be used.

APPENDIX A

Cost Estimates

The following cost estimates have been compiled using information gathered during the ground investigation and preliminary design stages of the projects. As the development of each project progresses the total project cost may rise or fall as design changes are made and external costs (utilities, SEPA, land acquisition) are firmed up.

Currently the total cost for all four schemes is in the region of £4.4m, some £675k over budget.

Cost summary:

1. A859 Stockinish Junction to Luskentyre Junction £0.933m

2. A865 North of Kildonan Junction to Loch Roinich £0.981m

3. A865 Carinish Hall to Carinish Village £1.444m

4. A859 Kyles Lodge Entrance to Leverburgh Village £1.035m

APPENDIX A

APPENDIX A